A hydrosalpinx is a fallopian tube that is filled with serous or clear fluid. It is one of the common inflammatory diseases. Injury to the end of the fallopian tube, the ampulla, and its delicate fingers, the fimbria, causes the end of the tube to close. Glands within the tube produce a watery fluid that collects within the tube, producing a sausage shaped swelling that is characteristic of hydrosalpinx. Hydrosalpinx is a cause of infertility.

Hydrosalpinx is a result of injury to the tube, usually caused by an infection. The typical causes of hydrosalpinxare chlamydia and gonorrhea, slowly injuring the delicate fimbria. Artificial abortion, spontaneous abortion, artificial labor and pelvic infection often cause adhesion, hyperemia, and edema. IUDs, endometriosis, and abdominal surgery sometimes are associated with the disease. As a reaction to injury, the body rushes inflammatory cells into the area, and inflammation and later healing result in loss of the fimbria and closure of the tube. These infections usually affect both fallopian tubes, and although a hydrosalpinx can be one-sided, the other tube on the opposite side is often abnormal. Hydrosalpinx can often be found in cases of infertility.

Not only does a hydrosalpinx cause infertility, it can also reduce the success rate of fertility treatment, even those treatments are not associated with the fallopian tubes. The large volume fluid flow back into the uterus and can produce enough flow that embryos find it difficult to attach, since they have no ability to prevent this. The blocked tubecan communicate with the uterus, and the fluid in the tube can be expressed into the uterus from the tubes. This fluid is probably toxic to early embryo development, and certainly provides an bad environment.